We all experience pain, but scientifically what is it? Most of us think of pain as an unpleasant sensation that originates in traumatized tissues and warns of injury, but it also has emotional qualities. Ancient philosophers mostly considered pain an emotion. Aristotle, for example, called it a passion of the soul. A contemporary writer described pain's qualities as including extreme aversiveness, an ability to annihilate complex thoughts and other feelings, an ability to destroy language, and a strong resistance to objectification (Scarry, 1985). Her perspective resonates with the lessons of everyday life: while pain has sensory features and lends itself to sensory description, it is above all else a powerful and demanding feeling state. Put more simply, pain is in part an emotion. The standard definition for pain, as developed by the International Association for the Study of Pain is as follows: "An unpleasant sensory and emotional experience normally associated with tissue damage or described in terms of such damage."
From the viewpoint of scientific inquiry, pain poses a significant challenge on several fronts. First, we need to view it multidimensionally. Our tools allow us to study it intensively and effectively at the level of sensory neurophysiology, but we are stymied as soon as we attempt to address it as an emotion (the central neurophysiology of emotion is formidably complex and still a frontier). Consequently, we risk developing an unbalanced knowledge base, filled with detailed information on the sensory neurophysiology of pain but void of content about pain's emotional nature. Second, pain is by definition a phenomenon of consciousness. It does not exist outside of the realm of awareness: it is not an observable phenomenon, it has no objective markers and it defies objective measurement. Our methods for measuring pain subjectively (recording reports of its quality, intensity, time course, and personal meaning) are primitive at best. Finally, we face a significant challenge in reconciling the progress in basic science areas with clinical application that improves pain control. For example, over the past two decades we have witnessed the publication of thousands of papers on endorphins along with elegant theory and speculation about the role of endorphins in pain and pain relief, but this has not led to a single drug or other product that improves the care of patients with pain. In this and many other areas, a gap exists between what we think we know and what we can achieve on the battlefield of clinical care. The answer, I suspect, lies with developing a truly multidisciplinary basic science and with integrating pain research with emerging research efforts in the fields of emotion and consciousness.
When one deals with pain as a clinical problem, subtle issues of definition take on enormous importance. Many physicians still hold the anachronistic and overly simplistic view that pain is merely an aversive sensation (a sensory problem). The usual therapeutic solution to an aversive sensation is to turn it off in one of the following ways: remove the origin of the noxious signaling, gate signal transmission from the peripheral tissues with opioid or other drugs, prevent such transmission with temporary nerve blocks, or introduce destructive lesions within the nervous system that prevent such transmission. This level of understanding, while not all wrong, is clearly incomplete. Pain proves notoriously unresponsive to conventional therapies that target its putative cause, can appear and persist without evidence of tissue trauma, and above all else it envelops the whole of the person who experiences it, interfering with normal living, functional capability and sleep. Recognizing this, Chapman and Stillman (1996) defined pathological pain as "severe persisting pain or moderate pain of long duration that disrupts sleep and normal living, ceases to serve a protective function, and instead degrades health and functional capability.." Because persisting pain causes true suffering, clinical intervention directed at pain needs to address the entire person -- protecting functional capability, psychological well being and overall health.
Scarry, E. (1985) The Body in Pain: The Making and Unmaking of the World, Oxford University Press, New York.
Chapman CR, Stillman M: Pathological Pain, Handbook of Perception: Pain and Touch. Edited by Krueger L. New York, Academic Press, 1996, pp 315 - 340
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